This invention relates to the protection of recording of a magnetic recording medium and more particularly, it is concerned with the provision of a magnetic drum, magnetic disk or like with a protective layer by an electroplating or electroless plating method.
In a magnetic recording apparatus of the prior art using a ring type head for recording or reproducing, it is important in order to increase the recording density to bring the magnetic head into contact with a magnetic layer as smoothly and tightly as possible, but the recording or reproducing is continued at a rate of 5 to 40 m/sec with holding the contact of the magnetic head and magnetic layer, resulting in that both the magnetic head and magnetic layer are worn and the recording or reproducing becomes impossible often. Therefore, there have hitherto been proposed various methods, for example, wherein a magnetic layer itself is hardened or a magnetic recording layer is protected with a hard non-magnetic film of rhodium or chromium having a thickness of 0.05 to 3 microns by plating or by vapor deposition. As a further improved method, it is proposed to coat such a hard film surface with a lubricating material such as silicone resin, grease, stearic acid or oleic acid in a thickness of about 0.05 to 1 micron.
However, these known methods have the following disadvantages:
1. A protective layer obtained by the hard plating method is so hard and brittle that it tends to be broken by a rapid force and a magnetic layer or head tends to be scratched by its fragments.
2. The method of hardening a magnetic layer itself has the disadvantage, in addition to the above described disadvantage (1), that a stable processing is difficult since the thickness thereof is below 1 micron. PA1 3. The coating of a lubricant such as silicone resin tends to be stripped by a high speed friction and, accordingly, the effect thereof cannot be expected for a long period of time.
The inventors have made efforts to solve these problems and to lengthen the life of a magnetic recording medium and head.